analyze packet loss with wireshark

Lost packets can extremely slow down a network and even completely bring down at high load.

Poorly laid cables, network segments that are too long (above but also below 100 meters) but also too many switches can cause the network to become out of sync.

With Wireshark you can easily test your own connection for lost packet segments and retransmissions:

  • tcp.analysis.lost_segment – Indicates we’ve seen a gap in sequence numbers in the capture. Packet loss can lead to duplicate ACKs, which leads to retransmissions.
  • tcp.analysis.retransmission – Displays all retransmissions in the capture. A few retransmissions are OK, excessive retransmissions are bad. This usually shows up as slow application performance and/or packet loss to the user.

some lost segments to web destinations are ok, but massive lost packets on connections to a local server are bad.

OSX homebrew: MidnightCommander not working as root

Problem

bash-3.2$root# mc
common.c: unimplemented subshell type 1
read (subshell_pty...): No such file or directory (2)

solution – install newest bash

user$ brew update
user$ brew upgrade
user$ brew install bash
user$ /usr/local/opt/bash/bin/bash
user$ sudo bash -c 'echo /usr/local/opt/bash/bin/bash >> /etc/shells'
user$ chsh -s /usr/local/opt/bash/bin/bash
user$ sudo chsh -s /usr/local/opt/bash/bin/bash

debian9 mariadb: login nicht möglich

Manchmal sitzt man mehrere Stunden an einem Problem und findet keine Lösung.

Zwei nächte drüber schlafen und

phpmyadmin: mysqli_real_connect(): (HY000/1045): Access denied for user UserName@localhost (using password: YES)

Lösung
Benutzer und Datenbank neu anlegen, ohne Großbuchtsben im Nutzernamen und DB-Namen.

Und wenn der Import einer alten mySQL DB mit folgendem Fehler ab bricht:

#1118 - Row size too large (> 8126). Changing some columns to TEXT or BLOB or using ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED may help. In current row format, BLOB prefix of 768 bytes is stored inline.

dann hilft ein 

innodb_file_per_table=1
innodb_file_format = Barracuda

in der my.cnf mit anschließendem Neutstart/reload des DB-Servers.